Petroleum conversion



Nov. 3, 1936. vv. KAPLAN PETROLEUM CONVERSION l Filed'April 1; 1935 l l l RNVENTOR WILLUAM KAPLAN ATTORNEY Patented Nov. 3, 1936 UITED STATES PATENT OFFICE PETROLEUM CONVERSION Application April 1, 1935, Serial No. 14,006

8 Claims.

This invention relates to improvements in process and apparatus for cracking hydrocarbon oils and more particularly to certain refinements in the control of the cracking operation.

In the high temperature oil cracking processes now in use, it is customary to effect a large part of the cracking in heated coils or in enlarged digestion` chambers at a high temperature and then suddenly reduce 4the temperature of the highly heated oil constituents prior to the fractionation of the resulting vapor products. In many cases this sudden chilling or quenching operation is effected in the transfer line from the cracking coils or chambers by the introduction of a relatively cool oil or other fluid. Considerable diiiiculty has been encountered in operations of this type because of the formation of coke in the transfer line immediately preceding the point of introduction of the cooling fluid, and it is therefore an object of the presentinvention to overcome this difficulty and provide a process and apparatus Which will operate without the formation of coke in the transfer lines. The cause of the coke formation in the transfer lines has been found by investigation to be largely due to the cooling of a portion of the line by the rapid transfer of heat from the section of the line immediately preceding the point of introduction of the cooling fluid.

The invention therefore includes the utilization of certain process steps or means for preventing the cooling of the hot section of the transfer line adjacent the point of introduction of the cooling fluid. An effective means for accomplishing this result comprises a transfer line in which the cooling fluid is introduced into a section thereof which is insulated in such a manner that the cooling uid does not cool the hot part of the line.

Additional features and objects of the present invention will be apparent from the following detailed description thereof taken in connection with the accompanying drawing in which:

Fig. l is a diagrammatic flow sheet of an apparatus adapted to crack petroleum oils and in which the features of the invention are illustrated.

Fig. 2 is an enlarged detailed sectional view of a specific part of the apparatus shown in Fig. 1 illustrating one form of the apparatus comprising a part of the present invention.

Fig. 3 is an enlarged sectional view of a modified form of the invention shown in Fig. 2.

Fig. 4 is an enlarged sectional view of a modif fied form of apparatus illustrating a specic arrangement for preventing coking of the transfer line.

In order to illustrate the features of the invention the cracking of a hydrocarbon distillate such as a gas oil Will be described in connection with 5 Fig. 1 of the drawing. The gas oil to be cracked is introduced into the cracking apparatus of Fig. l through a line 2 and forced by means of a pump i and a line Ii into and through a plurality of tube banks 8, II) and I2, mounted in a pipe still furnace I3. In the coils the oil is heated and subjected to cracking conditions fo-r the desired length of time. The oil is preheated in the tube bank 8, raised to the cracking temperature in the bank I0 and maintained at the cracking 15 temperature for the desired length of time in the tube bank I2. The highly heated cracked products, which may be at a temperature of from 925 to 1150o F. and under a pressure of from atmospheric to 600 lbs. per sq. in., are discharged through a valved transfer line I4 and introduced into an enlarged chamber I6.

When the chamber I5 is merely used as a liquid-vapor separator the highly heated and cracked products are suddenly chilled in the line I4 to a temperature below that at which coke will deposit, and the separated liquid residue is withdrawn through a valved line I8. The cracked vapor products separated in the chamber I6 are conducted therefrom through a valved vapor line 22 into a fractionating tower M in which the higher boiling constituents of the vapors are fractionated out, and the gasoline or motor fuel fraction is taken overhead from the tower 24 through a valved vapor line 26. The gasoline fraction is condensed in a condenser 28 and conducted to storage through a line 3U. In this type of operation reflux condensate' produced and collected in the tower 24 is withdrawn therefrom through a line 32 and may be conducted to sto-rage or to another cracking unit through a valved line 34, or reintroduced into the cracking tubes I and I2 by means of a pump 36, through a line 38 and the line 6.

The cracking of certain oil stocks or the production of certain types of products may be satisfactorily and effectively accomplished in the tube banks 8, I0 and I2 so that the enlarged chamber I6 may be used exclusively as a liquid-vapor separating chamber. In this case the high temperature oil products passing through the transfer line I4 are suddenly chilled to a temperature below that at which coke formation and deposition will occur. This chilling is effected in the element 40 mounted in transfer line I4. The

actual chilling of the high temperature products may be effectively done by introducing into the stream of such products in the element 40 of line I4, a chilling medium such as a relatively cool oil, water, steam or a gas. This cooling medium is preferably introduced under high pressure through a valved inlet line 42 in such a way as to quickly cool the cracked products through the temperature range at which any coking would occur.

The detailed construction of the cooling section of the line I4, the element 46 and the line 42, is shown in Fig. 4 in which unconnected free ends 44 and 46 of the line I4 are shown as projecting into enlarged metal housing 48 which is packed with porous insulating material 56. The cooling medium line 42 projects into the line I4 as shown and extends into the section 46 a substantial distance, so that the cooling medium is sprayed into the high temperature vapors as they enter the section 46. The end of the line 42 is preferably provided with a spray nozzle which is adapted to give a very fine spray or distribution of the cooling medium.

It will be noted that the sections 44 and 46 of the transfer line I4 have no metal connection with each other except for the roundabout connection made by the housing 48. These sections of the transfer line I4 are therefore suitably insulated so that the cooler section 46 cannot abstract heat from the high temperature section 44. Furthermore the injection of the cooling medium is effected in such a manner that none of it comes in contact with the high temperature section 44. It is advantageous to introduce a gas into the housing 48 and diffuse it through the porous 'neat insulating material 50. Such a gas may be introduced through a valved line 52. The diffusion of the gas through the porous insulating material 56 prevents the porous insulation from becoming oil soaked, which would decrease its insulating value, thereby preventing the transfer of heat from one end of the housing 48 to the other, since the gas must flow into the section 46 of line I4 through the space between the sections 44 and 46. The arrangement and operation is therefore such that a very high temperature (925 to '75" F. or higher) is maintained right up to the end of the section 44, while an entirely different and much lower temperature (800 to 450 F.) is maintained from the inlet end of section 46. The insulating gas may be used without the insulation 5D to prevent heat transfer between the sections of the line I4.

Where the cracking operation carried out in the apparatus illustrated in Fig. 1 is such that the enlarged chamber I6 is used as a high pressure carbon settling and vapor phase cracking chamber, the highly heated and cracked products are preferably suddenly reduced in temperature immediately at the vapor outlet of the chamber I6. Fig. 1 therefore alternatively shows a quenching element 54 provided with a cooling medium inlet line 56 at the intake of the vapor line 22. The element 54 is shown in enlarged detail in Fig. 2 which embodies certain of the features of the construction shown in Fig. 4 described above. In Fig. 2 the enlarged housing 54 connects directly into the chamber I6, and the inlet end 58 of the Vapor line 22 extends through the housing to approximately the inner face of chamber I6 without contacting the chamber or the housing. As shown in Fig. 2, the section 58 of the vapor line 22 is substantially spaced from the housing 54 and its sides completely surrounded by insulating material 68. The cooling fluid line 56 extends into the vapor line 22 and throughout substantially the length of the section 58 so that the cooling medium is sprayed or distributed directly into the vapors as they enter the section 58. The construction shown in Fig. 2 therefore provides means for suddenly chilling the high temperature vapors and at the same time avoids the coking up of the vapor outlet line from the chamber I6 or the deposition of coke around the outlet line on the walls of the chamber. This is accomplished because there is no abstraction of heat from the walls of the chamber I6 to the much cooler metal walls of the section 58 Where the temperature is much too low for coke formation. If desired a gas may be introduced into the heat insulating material 60 in the manner shown in Fig. 4, if the insulating material is of a porous character, or gas may be used exclusively as the insulating material in the casing 54.

The sudden cooling of the vapors as they discharge from the chamber I6 as illustrated in Fig. 2 is highly advantageous because the formation of coke in vapor line 22 is definitely prevented. The placing of the spray nozzle within the section 58 prevents coke from building up in the relatively cool line 56, which coking would occur if the line 56 were positioned within the chamber and exposed to the hot cracked vapors.

Instead of providing the vapor chilling element directly at the inlet of the vapor line 22y it may be alternatively placed in the bend immediately prior to the introduction of the vapors into the fractionating tower 24. A chilling section or element 62, including a valved cooling fluid line 64, is inserted in the vapor line 22 to illustrate this feature of the invention. In this type of operation the chilling may be eifectively accomplished in the lower part of the line 22, as by means oi the element 62 which is illustrated in enlarged sectional detail in Fig. 3 of the drawing. In this construction the horizontal portion of the line 22 is provided with an extended section 66 which projects into the mid-portion of the housing 62. The section 66 is substantially spaced and insulated from the housing 62 by means of heat insulation 68. The cooling fluid line 64 extends into the housing 62 through the insulation 68, so that its nozzle is directed into the open end of the section 66 as shown. The high temperature vapors passing downwardly through the vertical section of the line 22 into the housing 62 are suddenly chilled as they enter the section 66 and the construction is such that heat is not abstracted from the housing or inlet portion of line 22, by the relatively cool pipe section 66 of the line 22 or the line 64. A gas may be introduced into the heat insulating material 68 in the manner illustrated in Fig. 4.

When the high temperature vapors are chilled in the line 22, the liquid and vapor products are discharged together from the line 22 into tower 24, and the unvaporized residue is withdrawn to storage or to a flash still through the line 34, while reux condensate is withdrawn from the tower 24 through a line (not shown) from a point immediately above the line 22.

It is to be understood that the various parts of the apparatus shown in the drawing are to be insulated and particularly those which are at high temperatures. The housings 48, 54 and 62 are to be insulated exteriorly in addition to the insulation which they contain. While flanges and other types of connections and types of construction are shown in Figs. 2, 3 and 4, it is to be understood that the various parts of these elements of the apparatus may be welded together or assembled in any other convenient manner so long as they embody the features of the invention.

Having thus described the invention in its preferred form, what is claimed as new is:

1. An oil cracking apparatus comprising a pipe still furnace for heating and cracking oil, means including a transfer line for conducting the highly heated oil products from the pipe still to fractional condensing equipment, means in said transfer line for suddenly chilling the highly heated oil products passing therethrough, said chilling means including a cooling medium supply line and a spray nozzle adapted to spray cooling medium into the transfer line, and means including heat insulation for preventing the transfer of heat from the portion of the line on the high temperature side of said spray nozzle to the portion of the line on the cool side of the spray nozzle.

2. An oil cracking apparatus as defined by claim 1 in which said chilling means includes an enlarged section of the transfer line, lined with heat insulating material arranged to prevent the transfer of heat from the transfer line on the high temperature side of the spray nozzle to the portion of the transfer line on the low temperature side of the spray nozzle.

3. An oil cracking apparatus comprising a pipe still furnace for heating and cracking oil, means including a transfer line for conducting highly heated oil vapors from the heating portion of the apparatus to the fractional condensing equipment thereof, means in said transfer line for suddenly chilling the highly heated vapors passing therethrough, said transfer line including an enlargement, a section of transfer line extending into said enlargement and being surrounded with insulating material, and means for spraying a cooling medium into the portion of the transfer line extending into said enlargement.

4. In an oil cracking apparatus including heating and cracking equipment and fractionating equipment in which a transfer line is provided for conducting high temperature cracked vapors from said heating and cracking equipment to said fractionating equipment, the improvement which comprises a transfer line having an enlarged section into which a, portion of the line of smaller diameter extends for a substantial distance, heat insulating material mounted between said extended smaller diameter portion and said enlarged section, said line being arranged in such a way that high temperature vapors enter said extended end f smaller diameter, and means for spraying a cooling medium into the vapors in the extended end of said transfer line projecting into said enlarged section.

5. In the process of cracking hydrocarbon oils for the production of high anti-knock motor fuels in which an oil is heated to a high temperature and cracked in vapor phase and the resulting products thereof suddenly chilled to a relatively low temperature in a metal vapor transfer line, the improvement which comprises suddenly chilling the high temperature vapors in the transfer line by introducing thereinto a sufficient quantity of cooling medium', and preventing the coking up of the transfer line in advance of the point of introduction of the cooling medium by preventing the transfer of heat by conduction from the section of the transfer line in advance of the point of introduction of the cooling medium to the section of the transfer line at and beyond the point of introduction of the cooling medium.

6. The process defined by claim 5 in which the transfer of heat from the high temperature section of the transfer line to the low temperature section of the transfer line is prevented by introducing and distributing a fluid heat insulating medium into the line between these sections.

7. An improved transfer line for conducting highly heated hydrocarbons to vapor treating equipment which comprises a transfer line having an elongated enlarged section, an extension of the transfer line of smaller diameter than said enlarged section extending into each end of said enlarged section a substantial distance, the ends of said extensions being in spaced relation with respect to each other, heat insulating material mounted around said extended ends inside the enlarged section, and means for distributing a cooling medium into the extended end of one of said extended sections, said transfer line being arranged in such a way that the high temperature hydrocarbons pass from the hot extension into the extension receiving the cooling medium.

8. An improved transfer line as defined by claim 7 in which means is provided for introducing a gas into said enlarged section to aid in preventing heat transfer from the hot extended end to the extended end receiving the cooling medium.

WILLIAM KAPLAN. 

